The minor elements, Si (-5.81%), Cu (7.18%), Ge (14.76%) and Sri (74.08%)were chosen to investigate the effects of volume size factor as shown in the parentheses on void swelling in neutron irradiated Ni alloys. Neutron irradiation temperature and dose were changed widely from 473 K to 703 K, and 0.001 dpa to I dpa, respectively. Voids were observed by transmission electron microscopy (TEM) in Ni even after a very small irradiation dose of 0.026 dpa at 573 K. With increasing dose, the number density of voids was nearly constant while void size increased. The microstructure evolution in Ni-2at%Cu and Ni-2at%Ge alloys was similar to that in Ni. However, in Ni-2at%Si and Ni-2at%Sn alloys, no voids were observed by TEM even at 703 K to I dpa. The minor elements, Si and Sri, play an important role for the suppression of vacancy clusters. Vacancies are annihilated by mutual recombination with interstitials in Si and Sri added alloys.